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On Duties

Cicero

Roman republicanism / natural law

The most influential work of practical ethics ever written, and the bridge between Greek philosophy and the Western political tradition. Cicero argues that what is honourable and what is truly useful can never really conflict — that justice, duty, and the common good must govern public life. It shaped Christian, Renaissance, and Enlightenment thought, and the American founders read it closely.

About the author

Roman statesman, orator, and philosopher (106–43 BC), the supreme stylist of Latin prose and a defender of the Roman Republic against the rise of one-man rule. Cicero transmitted Greek philosophy to the Latin West and was murdered for opposing Mark Antony; his political and ethical writings remained central to European education for nearly two thousand years.

Synopsis

Written as a letter of advice to his son in 44 BC, in the dying days of the Roman Republic, On Duties (De Officiis) examines what we owe one another. Cicero treats the honourable (wisdom, justice, courage, temperance) and the useful, and argues at length that they cannot genuinely conflict: apparent gains won by injustice are never truly advantageous. He grounds duty in a natural law binding all human beings.

Core passage idea

Paraphrase · Public domain

Cicero argues that nothing which is dishonourable can ever be truly useful, because justice and the common good are inseparable from real advantage.

By denying that injustice can ever really pay, Cicero refuses the separation of ethics from politics that later realists embrace. It is the classic statement of the view that a healthy republic depends on citizens and rulers who treat honour and the common good as binding, not optional.

To avoid a bubble

Pair with Machiavelli's The Prince, the deliberate inversion of Cicero, which argues that a ruler must sometimes set aside honour and justice for the sake of results and survival.

Reading note

Read Book I (the honourable) and Book III (the apparent conflict of the honourable and the useful) as the heart of the argument. Then read The Prince directly against it — Machiavelli wrote, in part, to refute exactly this book.

Best paired with

Niccolò Machiavelli, The Prince; Marcus Aurelius, Meditations.

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